CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) as the name suggests are used to differentiate automated computer programs or bots from humans. CAPTCHAs are used for various purposes such as preventing automated account creation on websites, prevention of traffic flooding on websites and spam-protection etc., but CAPTCHAs deny access to visually impaired humans as well. Most visually impaired people use narration softwares, so visual CAPTCHAs deny access to those considering them as bots. Audio CAPTCHAs help the visually impaired people pass the test, though they possess major challenge as bots may pass such a CAPTCHA by voice to text translation. Hence, some trivial or lingual techniques need to be employed in order to make them effective against bots but easy to crack for humans.